The following example evaluates the efficiency of changing the decimal format of a numeric field to eliminate synonyms.
Assume that column_1 and column_2 are declared as DECIMAL(2,2).
You can determine the effect of reformatting the columns to DECIMAL(8,6) and DECIMAL(8,4) on hash collisions by submitting these two queries.
SELECT COUNT (DISTINCT column_1(DECIMAL(8,6)) || column_2(DECIMAL(8,4)) FROM T; SELECT COUNT (DISTINCT HASHROW (column_1(DECIMAL(8,6)), column_2 (DECIMAL(8,4))) FROM T;
If the result of the second query is significantly less than the result of the first query, there are a significant number of hash collisions. That is, the closer the second result is to the first value indicates elimination of more hash synonyms.